Initial x-ray absorption studies performed under Rapid Turnaround XAS proposal 1E23 showed that XAS is sensitive to the different Cd environments on the cell wall and in a metal-binding polypeptide from metal-tolerant Datura innoxia tissue culture. These studies suggest that it may be possible to use XAS to follow the in situ transformation of heavy metals by metal-accumulating plants. Based on these results, we propose to extend this work to characterize the Ni and Cr sites on D. innoxia cell walls and in metal complexes isolated from D. innoxia plant cells. We also propose to use XAS to follow the in situ transformation of Cd by D. innoxia tissue culture. These studies will provide insight into the transformation of metal ions by metal-tolerant plants on a cellular level, and contribute to an understanding of the biotic transformation pathways that contribute to the fate of metal ions in the environment.